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Renal Function Assessment (Residual Function Evaluation)

Published: August 9, 2026Updated: August 16, 2026

This test evaluates how well your kidneys are functioning after treatment or surgery, often done to monitor ongoing kidney health.

Quick summary

["Helps track kidney performance post-intervention or chronic conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
70950-1
Short code
RESIDUALRENALFUNCTIONTESTINGPERFORMED
Synonyms
—
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
esrd
CPT
86430
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

This test assesses residual kidney function by measuring specific markers that reflect how well your kidneys are filtering waste and maintaining fluid balance. It may include blood tests to evaluate kidney-related substances or urine tests to check for ongoing filtration capacity.

Why It’s Done

Your healthcare provider may order this test if you’ve had kidney surgery, received dialysis, or are managing chronic kidney disease to ensure your kidneys are still working effectively and to adjust treatment as needed.

Common Tests Included

While the exact tests vary by lab, this evaluation often includes blood tests for substances like creatinine clearance, electrolytes, or other kidney-specific markers, or urine tests for protein or other indicators of kidney function.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for certain blood tests or to provide a urine sample at a specific time. Follow your provider’s instructions carefully.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test helps determine if your kidneys are retaining enough function after medical intervention. Low or declining results may signal ongoing kidney strain, requiring closer monitoring or adjustments to your care plan.

Short name

Renal Function Check

Frequently asked questions

Will this test show if my kidneys are damaged permanently?
This test evaluates *current* kidney function, not permanent damage. It helps track trends over time but doesn’t directly measure irreversible damage. Follow-up tests may be needed for long-term assessment.
How long will I need to wait for results?
Results typically arrive within 1–3 business days, depending on the lab and tests performed. Your provider will contact you once they’re ready.
Can I drink water before this test?
For blood tests, you may drink water but avoid fluids for 2–4 hours before collection. For urine tests, follow specific instructions (e.g., first-morning void or timed collection). Always check with your provider.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy